This invention relates generally to ink jet print heads and more particularly concerns multicolor ink jet print heads in which the inks must be fed in isolation from one another to separate nozzles.
In a monochrome ink jet print head, liquid ink is contained in the interior of a print head body, perhaps retained within a foam material. If the print head is arranged for operation so that the nozzle assembly is at the bottom of the print head, for example, an exit port is provided in the bottom of the print head body to allow ink to flow to the nozzle assembly. In the case of a thermal ink jet printer, the nozzle assembly includes a heater chip and nozzle plate which cooperate to form an ink supply area downstream of the exit port and channels running to individual nozzle openings for the emission of ink drops to effect printing.
A multicolor ink jet print head contains a number of separate ink-containing chambers separated from one another by walls in a print head body. For example, a three color print head for cyan, magenta and yellow inks includes three separate ink chambers, each of which would typically include an individual foam element for the ink therein.
It is an objective in multicolor print heads of this type to avoid any intermixing of the different colors of ink. In doing this, the ink flow design must accommodate close proximity of three separate exit ports from the print head body to three different sections or areas of a nozzle assembly. For reasons of nozzle assembly manufacture, it is preferred to have the three nozzle arrays for the three colors of ink closely adjacent one another using a single heater chip.
In one known print head body fabrication technique, the bottom of the print head body is formed by ultrasonicly joining a plastic nose piece onto a plastic body part to form the bottom of the print head body. The various flow channels for the three colors of ink are formed cooperatively between the facing surfaces of the nose piece and the body.
This type of assembly requires precise placement of the nose piece relative to the print head body and also runs the risk of leakage of ink at the ink flow passage-defining walls formed when the nose piece is bonded to the body part.
It is a general objective of the present invention to provide a print head in which the print head body is more readily manufacturable and assures isolation of the different colors of ink.
In carrying out the invention, a print head body is employed which includes side and interior walls and a bottom to define at least two separate ink chambers and at least two exit ports in the bottom of the print head body for supplying ink to a nozzle assembly. Included is at least one crossflow channel in the bottom of the print head body which communicates with one of the exit ports and also with an opening in the bottom of one of the ink chambers.
In one form of the print head body, there are three ink chambers and the bottom of the print head body includes two crossflow channels, each communicating between a separate exit port and a different ink chamber in the print head body.
In the illustrated form of the invention, each cross channel is originally formed to extend to the exterior of the print head body and subsequently sealed with a plug inserted into the end of the crossflow channel.
Advantageously, since the crossflow channels are formed completely separately from one another, and without being defined by a process of mating one surface with another, there is complete isolation of the inks flowing through the crossflow channels.
As will be described in more detail subsequently, the exit ports, chamber openings, and crossflow channels are formed in the bottom portion of a unitary print head body during an injection molding operation.